It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) came one day to perform the ritual bath (ghusl). One of his wives said: "O Messenger of Allah! This is the water left over from a ritual bath." He (peace and blessings be upon him) said: "Water does not become impure."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11665